The Swami Thumb writer may appear to be nothing more than a grease marker attached to your thumb, but effects that can be done with it are astounding. For example, the magician asks a spectator to think of a 3 digit number. The magician writes his prediction on a piece of paper. When the spectator announces out loud the 3 digit number, the magician can show the piece of paper featuring the same number!

This wonderful device is very useful for mental magic or any occasion where you want to write something down without having it look like you are writing anything down.